Poly(oxyalkylene) polymeric colorants have been utilized to permanently color myriad substrates, including thermoplastic resins, such as U.S. Pat. No. 4,284,729, to Cross et al., U.S. Pat. No. 4,507,407, to Kluger et al., and U.S. Pat. No. 4,751,254, to Kluger et al.; polyurethane foams, such as U.S. Pat. No. 4,846,846, to Rekers et al.; aqueous and non-aqueous liquids, such as U.S. Pat. No. 4,871,371, to Harris; and have been used as fugitive tints for textiles and threads, such as U.S. Pat. No. 4,167,510, to Brendle. Such colorants provide effective and stable colorations to such materials, are easily handled, and exhibit desirable migratory properties within certain substrates.
Colorants have been developed for utilization within polymer resins, including in polyester (polyethylene terephthalate, for instance), such as U.S. Pat. Nos. 4,332,587, to Kresser et al., 4,640,690, to Baumgartner et al., 4,732,570, to Baumgartner et al., 4,812,141, to Baumgartner et al., 5,157,067, to Burditt et al., 5,240,980, to Danielson et al., 5,326,516, to Branon, 5,443,775, to Brannon, and 5,686,515, to Phillips et al. The primary method of coloring such thermoplastics has been through the utilization of a color concentrate. Such a concentrate is basically comprised of colored polymer chips which, when introduced within a standard extrusion or injection molding process, melts with the subject resin pellets and subsequently colors the molten plastic upon mixing. Although this procedure is the primary manner of coloring thermoplastics, it also possesses certain disadvantages which have created problems in the past. For instance, the colorants themselves must be able to sustain dispersing during at least two distinct stages, namely the production of the concentrates polymer chips and then the coloring of the subject thermoplastic resin. Because of the need to form an initial concentrate, the colorant must also withstand high temperatures in the polymer chip formation and then, again, during the creation of the molten resin. Such high temperatures may degrade the colorant and subjecting such compounds to two distinct stages of melting increases the possibility of colorant loss.
A secondary procedure has also been utilized to color such thermoplastic articles. This procedure entails the introduction of a liquid colorant into an extrusion or injection molding machine simultaneously with subject resin pellets or chips, and the like. This method is preferable to the color concentrate because it is cost effective (there is no need to produce initial colored polymer chips), subjects the colorant to only one period of high temperature exposure, and allows for easy handling of the colorant in liquid form. Liquid poly(oxyalkylenated) colorants provide excellent colorations within polyester thermoplastic articles and withstand high temperatures processing reasonably well. It has proven difficult, however, to incorporate such beneficially performing liquid poly(oxyalkylene) colorants into polyester thermoplastic compositions by this secondary straight introduction method and also produce suitable aesthetically pleasing colorations within such substrates. The Baumgartner et al. references, for instance, each teach the utilization of such colorants within polyester thermoplastics; however, undesirable streaks and specks are noticeable within the final colored resin products. The problem appears to be that such colorants are not thoroughly and uniformly incorporated within polyester when utilized on typical commercial-scale molding equipment. Nowhere within the prior art is there a teaching or fair suggestion as to how such problems can be remedied for liquid poly(oxyalkylene) colorants. As a result, there still exists a need for providing the optimum coloring benefits of polyoxyalkylenated polymeric colorants within polyester thermoplastic compositions through the straight introduction of a liquid colorant during the extrusion or injection molding process.